I really do love the hipstamatic and I know that I am repeating myself but:
These are old pictures from the summer, but they are some of my favs- mostly because of the effect. There are lots of "duds" taken with the hipstamatic- but I can't complain. So easy, quick and small to carry round. I've had some of them printed as well, and they come out fine. Not like the old school camera days when I gave up bothering opening the little lens and getting a dodgy pic even in good light.
I'll be trying out the http://pixlr.com/o-matic/ as Rosie at http://rosiescribble.typepad.com/rosie-scribble/ exampled.